Add timing keyword argument for hooks

Measure the duration of the sync operation in the Execute method of the
Sync command and pass it to post-sync hooks as a standard keyword
argument (`sync_duration_seconds`).

Updates based on code review:
- Update _API_ARGS in hooks.py to allow sync_duration_seconds for post-sync hooks.
- Do not cast sync_duration_seconds to int for better granularity.
- Update docs/repo-hooks.md to document sync_duration_seconds.
- Add unit test for argument validation in test_hooks.py.

Test: Ran run_tests using venv python, all 554 tests passed.
Bug: TBD
Change-Id: Ie29e002a5d283460d993ad96c224dbf4b6d7985c
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/575021
Tested-by: Arif Kasim <arifkasim@google.com>
Commit-Queue: Ram Peri <ramperi@google.com>
Reviewed-by: Arif Kasim <arifkasim@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

tests/test_hooks.py

@@ -14,6 +14,9 @@
 
 """Unittests for the hooks.py module."""
 
+from io import StringIO
+import sys
+
 import pytest
 
 import hooks
@@ -58,3 +61,47 @@ def test_direct_interp(shebang: str, interp: str) -> None:
 def test_env_interp(shebang: str, interp: str) -> None:
     """Lines whose shebang launches through `env`."""
     assert hooks.RepoHook._ExtractInterpFromShebang(shebang) == interp
+
+
+def test_post_sync_argument_validation() -> None:
+    """Test that post-sync hook requires exact API arguments."""
+
+    class FakeProject:
+
+        def __init__(self):
+            self.worktree = "/some/path"
+            self.enabled_repo_hooks = ["post-sync"]
+
+    hook = hooks.RepoHook(
+        hook_type="post-sync",
+        hooks_project=FakeProject(),
+        repo_topdir="/topdir",
+        manifest_url="https://gerrit",
+        allow_all_hooks=True,
+    )
+
+    old_stderr = sys.stderr
+    sys.stderr = StringIO()
+
+    try:
+        # Call with missing arg `sync_duration_seconds`
+        res = hook.Run(repo_topdir="/topdir")
+        assert res is False
+        assert "hook 'post-sync' called incorrectly" in sys.stderr.getvalue()
+
+        # Mock _CheckHook and _ExecuteHook to test success path
+        hook._CheckHook = lambda: None
+
+        executed_kwargs = {}
+
+        def fake_execute(**kw):
+            executed_kwargs.update(kw)
+
+        hook._ExecuteHook = fake_execute
+
+        res = hook.Run(repo_topdir="/topdir", sync_duration_seconds=12.345)
+        assert res is True
+        assert executed_kwargs.get("sync_duration_seconds") == 12.345
+
+    finally:
+        sys.stderr = old_stderr